Carcinogenic N-nitroso compounds may be formed in foods as a result of the reaction between amines and nitrite. Although the majority of previous studies have centered on the formation of the volatile N-nitrosamines, this group may constitute only a small proportion of the N-nitroso compounds to which man is exposed. It is therefore important to establish whether other N-nitroso compounds or their precursors are formed as a conseqence of the processing, cooking, or storage of foods. Conditions whereby such compounds may arise include the interaction of amino acids and amines with fatty acids, the interaction between oxidizing lipids and free amino compounds, and the thermal processing of foods containing large amounts of phospholipids. The principal objectives of this research are to study with model systems and then with special food systems, including meat, cheese, milk, and dried egg products, the conditions which contribute to the formation and occurrence of N-nitroso compounds or their precursors in food systems, and to evaluate the effect of various methods of thermal processing (spray drying, drum drying, pasteurization) and cooking (frying, broiling, microwaving) on the formation of such compounds. These compounds will be isolated, purified, and identified by chromatographic techniques with confirmation by mass spectrometry. The mutagenicity of these purified N-nitroso compounds will be evaluated using the Salmonella typhimurium assay.